The present invention relates to utilization of effluent gas from various industrial processes and particularly to recovery of effective components from the effluent gas.
Today, a large amount of effluent gas is generated from various sources including various industrial plants, various combustion apparatuses, laboratories, engines of automobiles and the like. The whole amount of these effluent gas is released into the atmosphere every day, and causes air pollution. The effluent gas generally includes at least one noxious gas pollutant, such as sulfur dioxide or nitrogen oxides of various forms. Attempt have been made to remove the pollutants from the effluent gas before releasing them into the atmosphere. For example, Machi et al., U.S. Ser. No. 431,925 discloses a process for removing SO.sub.2 and/or NO.sub.x from effluent gas which comprises irradiating the gas with an ionizing radiation to convert the SO.sub.2 gas and/or NO.sub.x gas contained in the effluent gas to an aerosol, and collecting the aerosol containing sulfur dioxide and/or nitrogen oxides to obtain the collected material.
However, a process for further treating the collected material has not yet been discovered. Therefore, when such collected material is dumped, it causes water pollution.
It has been found that when collected material is heated or is subjected to steam-roasting with or without addition of a suitable additive thereto, either effective components contained in the collected material or materials which are readily convertible to effective components by post treatment can be recovered. The present invention is formed on the basis of this discovery.
Therefore, it is an object of this invention to provide a process for separating sulfur compounds and nitrogen compounds as main components from the collected material.
Another object of this invention is to provide a process for separating sulfur compounds and nitrogen compounds from the collected material which comprises blending an alkali earth metal compound with the collected material and then forming a paste of the mixture, and subjecting the paste to steam-roasting, and then subjecting the resulting steam-roasted product to thermal decomposition, thereby removing nitrogen dioxide from the product.
Still another object of this invention is to provide a process for recovering effective components from the collected material which comprises blending the collected material with an ore of low quality (ore which contains so small an amount of effective contents that it is not worth being smelted), solid waste generated from smelting processes, or copper-containing pyrite cinders, and forming a paste of the mixture, and subjecting the paste to steam-roasting.
Another object of this invention is to provide a process for recovering a mixed acid of sulphuric acid and nitric acid from the collected material which comprises forming a paste of the collected material, and subjecting the paste to steam-roasting.